How to use the reftools/lib/isref.js.isRef function in reftools

function inner(obj,key,state){
            if (obj[key] && isRef(obj[key],'$ref')) {
                let $ref = obj[key].$ref;
                if (!$ref.startsWith('#')) { // is external

                    let $extra = '';

                    if (!refs[$ref]) {
                        let potential = Object.keys(refs).find(function(e,i,a){
                            return $ref.startsWith(e+'/');
                        });
                        if (potential) {
                            if (options.verbose) console.warn('Found potential subschema at',potential);
                            $extra = '/'+($ref.split('#')[1]||'').replace(potential.split('#')[1]||'');
                            $extra = $extra.split('/undefined').join(''); // FIXME
                            $ref = potential;
                        }
                    }

function fixupRefs(obj, key, state) {
    let options = state.payload.options;
    if (isRef(obj,key)) {
        if (obj[key].startsWith('#/components/')) {
            // no-op
        }
        else if (obj[key] === '#/consumes') {
            // people are *so* creative
            delete obj[key];
            state.parent[state.pkey] = clone(options.openapi.consumes);
        }
        else if (obj[key] === '#/produces') {
            // and by creative, I mean devious
            delete obj[key];
            state.parent[state.pkey] = clone(options.openapi.produces);
        }
        else if (obj[key].startsWith('#/definitions/')) {
            //only the first part of a schema component name must be sanitised
            let keys = obj[key].replace('#/definitions/', '').split('/');

recurse(openapi, {identityDetection:true}, function (obj, key, state) {
        if (isRef(obj,key)) {
            options.context.push(state.path);
            should(obj[key]).not.startWith('#/definitions/');
            let refUrl = url.parse(obj[key]);
            if (!refUrl.protocol && !refUrl.path) {
                should(obj[key]+'/%24ref').not.be.equal(state.path,'Circular reference');
                should(jptr.jptr(openapi,obj[key])).not.be.exactly(false, 'Cannot resolve reference: ' + obj[key]);
            }
            options.context.pop();
        }
    });

recurse(options.openapi,{},function(obj,key,state){
                                if (isRef(obj, key)) {
                                    if (!options.preserveMiro) delete obj['x-miro'];
                                }
                            });
                            res(options);